Humid tropical forests are often referred to as the lungs of the Earth. The long growing season and high plant biomass of these ecosystems helps regulate the chemical composition of the global atmosphere, and by extension, global climate. The availability of oxygen in soils and associated oxidation-reduction dynamics play important roles in carbon cycling and greenhouse gas fluxes in tropical forests. Changes in climate are likely to affect soil oxygen availability in tropical forests and in turn affect the flow of carbon and nutrients. Few studies have measured soil oxygen availability over time and space in tropical forests, and thus this important factor is absent or poorly represented in Earth systems models. In this study we will use field and laboratory experiments in humid tropical forests to develop a new component for the Community Land Model (CLM) that explicitly covers the relationships among soil oxygen, carbon cycling, and greenhouse gas fluxes. Research will be conducted in the Luquillo Experimental Forest, Puerto Rico. We will make near continuous measurements of soil processes to capture background patterns, as well as ‘hot spots’ and ‘hot moments’. The data and modeling efforts associated with this work will improve the prediction of carbon and nutrient cycling and greenhouse gas dynamics in humid tropical forests.